<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 250px;
            border: 5px solid red;
            overflow: hidden;
        }
        
        .one,
        .two,
        .three {
            width: 100px;
            height: 50px;
            background-color: brown;
            float: left;
        }
        
        .clear {
            clear: both;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="one">1</div>
        <div class="two">2</div>
        <div class="three">3</div>
        <!-- <div class="clear"></div> -->
    </div>
</body>

</html>